System and method for storing energy

ABSTRACT

A system includes at least one body, a link for suspending the body for movement with gravity from a first elevation position to a second elevation position, and an electrical energy generator coupled with the body through the link to drive the generator to generate electricity upon movement of the body with gravity from the first to the second elevation position. The at least one body has a mass of at least approximately 100 tonnes; the first and the second elevation positions define a distance therebetween of at least approximately 200 meters; and/or the system further includes an operator configured to operate the link to controllably move the at least one body against gravity from the second to the first elevation position to increase a gravitational potential energy of the at least one body, and to maintain the gravitational potential energy of the at least one body.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims priority to and the benefit of U.S. ProvisionalPatent Application No. 61/026,657, filed Feb. 6, 2008, U.S. ProvisionalPatent Application No. 61/081,340, filed Jul. 16, 2008, and U.S.Provisional Patent Application No. 61/140,921, filed Dec. 26, 2008, thecontents of all of which are incorporated herein by reference in theirentireties.

FIELD OF THE INVENTION

Embodiments of the present invention relate to systems and methods forstoring energy. Embodiments may be used, for example, to store energygenerated during “off-peak” periods (i.e., time periods during whichenergy demands are lower relative to “peak” periods) and/or energygenerated from renewable sources, such as, but not limited to, wind. Ina particular embodiment, an energy storage system is configured foroperation on land. In another particular embodiment, an energy storagesystem is configured for operation in an aquatic body, such as, but notlimited to, an ocean.

BACKGROUND

Providing adequate energy to power all the various needs of society isbecoming more problematic every year. Conventional sources such as coal,petroleum and gas, are becoming more expensive and harder to find. Atthe same time, the byproducts of combustion produce air pollution andelevate atmospheric carbon dioxide, threatening severe consequences forthe global environment.

A technology currently capable of providing high capacity energy storageis pumped hydro. An example of this technology is shown in the system 10of FIG. 1. With reference to FIG. 1, the system employs two large waterreservoirs 102 and 105 located at different elevations with respect toeach other. Water 106 is pumped by pump 101 from the lower reservoir 102to the higher reservoir 105 whenever excess energy is available, and theexcess energy (minus any losses due to inefficiencies) is stored in thesystem 10. (The excess energy is generated by power grid 108 and powerselectric motor 100 via substation 107.) Energy stored in the system 10is released as follows. Water 106 is released from the higher reservoir105 through hydraulic turbine 103 into the lower reservoir 102 toproduce mechanical energy. The mechanical energy is converted intoelectric energy by generator 104 and provided to the power grid 108 viasubstation 107.

Large-scale installations of systems such as system 10 can provide apeak output power of more than 1000 megawatts (MW) and a storagecapacity of thousands of megawatt-hours (MW-H). Pumped hydro has been acommon bulk storage technology for decades, providing capacityworldwide. However, geographic, geologic and environmental constraintsassociated with the design of reservoirs for such systems, in additionto increased construction costs, have made this technology much lessattractive for future expansion. Thus, this technology may not provide apractical method to provide the wide applicability, capacity, low costand environmental compatibility required to support the needs of futureexpansion, which may include, for example, a conversion of the energyinfrastructure from hydrocarbon sources to renewable sources of energy.

SUMMARY OF THE DISCLOSURE

Embodiments of the present invention are directed to energy storagesystems that can serve as reliable, dispatchable baseload powersupplies, as well as intermittent production supplies. In particularembodiments, the systems may harness renewable sources of energy, suchas, but not limited to, that collected by solar panels and windturbines. According to embodiments of the present invention, asignificant fraction of the output from solar- and/or wind-energydevices may be directed into large-scale energy storage units, which maythen release that energy as needed.

Relative to technologies such as pumped hydro, embodiments of thepresent invention are directed toward expanding the range of suitablelocations where energy storage can be carried out. Features ofembodiments of the invention include: high power potential (1000megawatts or more); large energy storage capacity (including, but notlimited to, 8 hours or more at rated power); minimization of adverseenvironmental impact; and proximity to power transmission lines or alarge electricity market, such as, but not limited to, a city.

In the case of pumped hydro, it may be difficult to locate sites capableof providing all or some of these features. Embodiments of the presentinvention are directed to expanding the range of suitable installationsites to exploit locations that exist in greater numbers near many ofthe major cities of the U.S. and the world.

According to one embodiment, a system for storing energy includes atleast one body, a link for suspending the at least one body for movementwith gravity from a first elevation position to a second elevationposition, and an electrical energy generator coupled with the at leastone body through the link to drive the electrical energy generator togenerate electricity upon movement of the at least one body with gravityfrom the first elevation position to the second elevation position. Theat least one body has a mass of at least approximately 100 tonnes; (b)the first elevation position and the second elevation position define adistance therebetween of at least approximately 200 meters; and/or (c)the system further includes an operator configured to operate the linkto controllably move the at least one body against gravity from thesecond elevation position to the first elevation position to increase agravitational potential energy of the at least one body, and to maintainthe gravitational potential energy of the at least one body.

According to another embodiment, a method for storing energy includesproviding a link for suspending at least one body for movement withgravity from a first elevation position to a second elevation position,and coupling an electrical energy generator with the at least one bodythrough the link to drive the electrical energy generator to generateelectricity upon movement of the at least one body with gravity from thefirst elevation position to the second elevation position. The at leastone body has a mass of at least approximately 100 tonnes; (b) the firstelevation position and the second elevation position define a distancetherebetween of at least approximately 200 meters; and/or (c) the methodfurther includes configuring an operator to operate the link tocontrollably move the at least one body against gravity from the secondelevation position to the first elevation position to increase agravitational potential energy of the at least one body, and to maintainthe gravitational potential energy of the at least one body.

These and other aspects will become apparent from the following drawingsand detailed description of exemplary embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a generalized schematic diagram of a pumped hydro energystorage system.

FIG. 2 is a generalized schematic diagram of an energy storage systemaccording to one embodiment.

FIG. 3 depicts an energy storage system according to one embodiment.

FIG. 4 depicts a salt dome.

FIG. 5 depicts an energy storage system according to one embodiment.

FIG. 6 depicts an energy storage system according to one embodiment.

FIG. 7 depicts an energy storage system according to one embodiment.

FIGS. 8A and 8B respectively show a top view and a side view of storageweights according to one embodiment.

FIG. 9 depicts a storage rack according to one embodiment.

FIGS. 10A, 10B and 10C illustration an operation of a grapple accordingto one embodiment.

FIGS. 11A, 11B and 11C depicts a friction drive hoist system accordingto one embodiment.

FIG. 12 depicts an energy storage system according to one embodiment,and

FIG. 12A shows a cross-sectional view of a buoyant platform according toone embodiment.

FIG. 13 depicts an energy storage system according to one embodiment.

FIGS. 14A and 14B respectively show a top view and a side view ofstorage weights according to one embodiment.

FIG. 15 depicts a storage rack according to one embodiment.

FIGS. 16A, 16B and 16C illustration an operation of a grapple accordingto one embodiment.

FIG. 17 depicts an energy storage system according to one embodiment.

FIGS. 18A and 18B respectively show a top and a side view of an energystorage system according to one embodiment.

FIGS. 19A, 19B and 19C illustrate an installation of an energy storagesystem according to one embodiment.

FIGS. 20A, 20B and 20C illustrate an installation of an energy storagesystem according to one embodiment.

FIG. 21 is a generalized schematic diagram of an energy storage systemaccording to one embodiment.

FIG. 22 is a generalized schematic diagram of an energy storage systemaccording to one embodiment.

FIGS. 23A and 23B illustrates an operation of an energy storage systemaccording to one embodiment.

FIG. 24 depicts an energy storage system according to one embodiment.

FIG. 25 depicts an energy storage system according to one embodiment.

FIG. 26 depicts an energy storage system according to one embodiment.

FIG. 27 depicts an energy storage system according to one embodiment.

FIG. 28 depicts an energy storage system according to one embodiment.

FIG. 29 illustrates a method of storing energy according to oneembodiment.

DETAILED DESCRIPTION

The following detailed description is of the best presently contemplatedmode of implementing embodiments of the invention. This description isnot to be taken in a limiting sense, but is made merely for the purposeof illustrating general principles of embodiments of the invention. Thescope of the invention is best defined by the appended claims.

Embodiments of the present invention relate to systems and methods forstoring energy that may be used, for example, to store energy generatedduring “off-peak” periods (i.e., time periods during which energydemands are less heavy relative to “peak” periods) and/or energygenerated from renewable sources, such as wind and the sun. Inparticular embodiments, methods and systems for storing energy areconfigured for operation on land. In other particular embodiments,methods and systems for storing energy are configured for operation inan aquatic environment, such as, but not limited to, in the ocean.

According to one embodiment, the energy demand of the “peak” period isconsidered to be about 50% higher than the energy demand of the off-peakperiod. According to other embodiments, the energy demand of the “peak”period can be defined at other suitable levels, including, but notlimited to, about 100% or 200% higher than the energy demand of theoff-peak period.

One aspect of the invention involves storing off-peak energy and/orrenewable energy for use during peak periods. As such, according toembodiments of the invention, energy storage systems can serve asreliable, dispatchable baseload power supplies, as well as intermittentproduction supplies. According to particular embodiments of the presentinvention, a significant portion of the output from solar and/or windsources are directed into energy storage systems, which may then releasethat energy, for example, on an as-needed basis.

A generalized diagram of a system 20 according to embodiments of thepresent invention is shown in FIG. 2. Example embodiments of the system20 are described herein with reference to land- and water-basedapplications. With reference to FIG. 2, a storage weight 202 issuspended by a link 205 for movement along a generally vertical path. Inparticular embodiments, the path is substantially vertical (i.e.,parallel to the direction of gravitational force). In other embodiments,the path may be angled, with a vertical component—e.g., the path isangled downward. In particular embodiments, the path may have a suitablevertical length such as, but not limited to, a length of around 1000meters or more. In a particular embodiment, the vertical length of thepath is around 6000 meters. According to one embodiment, the weight 202is constructed of a dense material such as, but not limited to,concrete, reinforced concrete and/or steel. According to particularembodiments, the mass of the weight 202 is at least approximately 100tonnes, or is at least approximately 1,000 tonnes. To reduce costs, thedense material may be a relatively low cost material. According toparticular embodiments, the link 205 may be any suitable connectionstructure such as, but not limited to, a cable, a wire, a rope, a beltor a chain.

An operator 201 is coupled with the link 205. The operator 201 operatesthe link 205 to move the weight 202 against gravity, as will bedescribed in more detail below. According to one embodiment, theoperator 201 is a hoist. The hoist 201 may be coupled with a motor 200for driving the hoist 201. In some embodiments, the motor 200 is coupledwith (or can operate as) the generator. The motor and/or generator 200may be coupled with the substation 203.

The substation 203 is for converting power from a “transmission” sourceto a “distribution” target. In more detail, the substation 203 mayinclude transformers that step transmission voltages (e.g., in the rangeof tens or hundreds of thousands of volts) down to distributionvoltages, which, for example, may be less than 10,000 volts. Thesubstation 203 may have a bus that can split the distribution power intomultiple directions. The substation 203 may also have circuit breakersand switches such that the substation 203 can be disconnected fromtransmission sources and/or distribution targets, if desired.

The substation 203 is coupled with an electric power transmitter, suchas, but not limited to, a power grid 204. The power grid 204 may serveas a source of power for the system 20. In other embodiments, the sourceof power may be one or more devices for capturing renewable energy suchas, but not limited to, a wind turbine or a solar panel. The power grid204 may also receive power released by the system 20 and carry thatpower to a target.

With continued reference to FIG. 2, in operation, power is provided bythe source, e.g., power grid 204. In embodiments where the power isprovided by an industrial source such as the power grid, the power istransformed by substation 203 for suitable use by the motor 200. Themotor 200 drives the hoist 201 to raise the storage weight 202 from afirst elevation (a location farther from the hoist 201) to a secondelevation (a location closer to the hoist 201). As such, thegravitational potential energy of the storage weight 202 is increased,and the increase in energy is stored in the system (e.g., by maintainingthe gravitational potential energy of the storage weight 202).

The stored energy is released when the storage weight 202 is lowered.The lowering of the storage weight turns the drum of the hoist 201,which effectively drives the motor/generator 200 to produce electricalenergy. The electrical energy is conditioned by the substation 203 fortransmission by the power grid 204.

As such, energy that is generated during off-peak periods (e.g., periodsof the days during which energy is in relatively low demand) may bestored in system 20 for later use (e.g., peak periods of the day duringwhich energy is in relatively high demand). For example, such off-peakenergy may be used to raise the storage weight 202 to the secondelevation during off-peak periods. As such, the off-peak energy (or asignificant portion of the off-peak energy) is stored in the system 20.The stored energy can be released during peak periods by releasing theweight 202 such that it falls back to the first elevation, therebyproducing energy for use during the peak periods.

The system 20 is configurable to store a desired amount (or desiredamounts) of energy. For example, a certain amount of energy can bestored in such a system, if the mass of the weight 202 and/or thevertical length of the path (i.e., the path along which the weight 202is lowered and raised) are configured accordingly. For example, in thecase of a weight made of concrete, because concrete has a density ofapproximately 2500 kilograms (kg) per cubic meter, such a weightprovides a downward force of about 24,525 Newtons (N) per cubic meter.The energy (work) released by lowering one cubic meter of concretethrough 1000 meters of elevation may be calculated as:W=Force×distance=24,525 N×1,000 m=24.525 megajoules=˜6.8 kilowatt-hours

According to one embodiment, the weight 202 is lowered (or raised) at agenerally constant speed such that the energy is released (or stored) ata correspondingly constant rate. According to other embodiments, theweight 202 is lowered (or raised) at two or more different speeds—forexample, at one speed during an initial 500 meters and at another speedduring the remainder of the path—such that the energy is released (orstored) at two corresponding rates. For example, during an initialportion of the path, the weight may be lowered at a certain speed, and,then, during a second portion of the path following the initial portion,the weight is lowered at half the speed of the initial portion. As such,during the second portion, energy is produced at a rate approximatelyhalf the rate at which energy is produced during the initial portion.This may correspond to a greater demand for energy during the time ofthe initial portion relative to the demand for energy during the time ofthe second portion. According to yet other embodiments, the lowering (orraising) of the weight 202 is accelerated or decelerated such that therate at which the energy is released (or stored) is also correspondinglyaccelerated or decelerated.

According to one embodiment, the storage efficiency (i.e., the ratio ofthe power that is generated by the system 20 to the power that is storedin the system 20) is improved by lowering the weight 202 at relativelymodest speeds to minimize (or at least reduce) drag losses incurred asthe weight 202 is lowered.

A side view of an embodiment of a system 30 that is installed on land isshown in FIG. 3. With reference to FIG. 3, a power house 305 issupported on the land surface 306. The power house 305 may be positioneddirectly on the land surface 306. In other embodiments, the power house306 may be positioned above the land surface—e.g., on a platform suchthat the power house rests above the land surface. The power house 305may be coupled with devices/systems such as the substation 203 and powergrid 204 of FIG. 2.

The power house 305 includes a hoist 301. The hoist 301 is coupled witha hoist cable 302 that may be wrapped around the drum of the hoist 301.A weight 303 is suspended by the hoist cable 302. In other embodiments,a belt or chain may be used in place of a cable to suspend the weight303. The weight is suspended such that it can be lowered and raisedwithin the shaft 304. As will be described in more detail below, theshaft 304 may be formed in a location such as, but not limited to, asalt dome. According to one embodiment, the orientation of the shaft 304is generally vertical (i.e., parallel to the direction of gravitationforce). According to other embodiments, the orientation of the shaft maybe angled with a vertical component corresponding to the angle.According to a further embodiment, the depth of the shaft 304 is betweenapproximately 1000 and 6000 meters.

Similar to the system of FIG. 2, the hoist 301 may be coupled to amotor/generator to produce electric power for transmission to a grid(e.g., power grid 204 of FIG. 2) via transmission lines. According to afurther embodiment, a gearbox is coupled between the hoist 301 andmotor/generator to multiply the motor/generator rotation rate. Accordingto yet another embodiment, a power conditioning system (e.g., powersubstation 203 of FIG. 2) is coupled between the motor/generator and thegrid to convert the generator output to a proper (or suitable) form fortransmission to the grid and/or to convert electric power from the gridinto the proper form to drive the motor.

With reference to FIG. 3, energy is stored in the system 30 when thehoist 301 is driven (e.g., using electricity from a power grid whichpowers the motor/generator) to lift the storage weight 303 againstgravity to a first elevation. Energy stored in the system 30 is releasedwhen the storage weight 303 is allowed to be released such that it moveswith gravity. Because the weight 303 continues to be coupled with thehoist 301 via hoist cable 302, the hoist 301 is turned when the weight303 moves down the shaft 304. The movement of the weight 303 turns thehoist 301, thereby generating power, as previously described.

As previously described with reference to FIG. 2, a weight of a systemmay be lowered (or raised) at two or more different speeds. Withreference to FIG. 3, in one embodiment, a speed at which the weight 303is raised by hoist 301 is controlled electronically. For example,according to one embodiment, a motor/generator for driving hoist 301 iscontrolled by a control circuit coupled with the motor/generator tocontrol the rate at which hoist cable 302 is drawn in by hoist 301.According to another embodiment, such a control circuit may be coupledwith the hoist 301 to control such a rate.

With continued reference to FIG. 3, in one embodiment, a speed at whichthe weight 303 is lowered by hoist 301 is controlled by configuring anoperating frequency of a generator (e.g., generator 200 of FIG. 2)coupled with the hoist. Configuring the operating frequency to be of acertain value correspondingly sets the speed at which the weight 303 islowered. Alternatively, if such a generator is synchronous with a powergrid (e.g., power grid 204 of FIG. 2), the gear ratio of a gearbox maybe configured to control the speed at which the weight 303 is lowered.For example, according to one embodiment, a gearbox may be coupledbetween the hoist 301 and the generator (see, for example, FIG. 21).Configuring the gear ratio of such a gearbox to be of a certain valuecorrespondingly sets the speed at which the weight 303 is lowered.

With continued reference to FIG. 3, in an alternative embodiment, aspeed at which the weight 303 is lowered by hoist 301 is controlled byor using a mechanical structure. For example, according to oneembodiment, a dampening structure (providing, for example, one or morelevels of dampening) is provided to control the rate at which hoistcable 302 is drawn out from hoist 301. Such a dampening structure mayinclude, but is not limited to, an adjustable clamp configurable toincrease the rotation resistance of the drum of hoist 301. According toanother embodiment, the hoist 301 includes a structure for setting sucha resistance (such as, but not limited, a screw that may be tightened orloosened). The dampening structure described above may be operablemanually (e.g., from a location accessible to a human operator) or by anelectronically controllable device such as an actuator.

Construction costs associated with the system 30 may be reduced, forexample, by, reducing the cost of constructing the generally verticalshaft (e.g., shaft 304 of FIG. 3). The costs associated withconstructing the shaft may depend upon the availability of subsurfacestrata through which such a shaft can be bored more easily.

According to one embodiment, the shaft is constructed in a site having asuitably large deposit of a relatively soft material—e.g., a softmineral. According to a particular embodiment, the shaft is constructedin a salt dome. Salt domes are salt deposits that, for example, can havea cross-sectional diameter of ten kilometers and a depth of sixkilometers (or more). They may consist primarily of crystallized sodiumchloride (i.e., rock salt), which is a very soft mineral.

With reference to FIG. 4, a cross-sectional view of a site having a saltdome 400 is shown. The salt dome may be located adjacent to multiplelayers of subsurface strata. The layers of subsurface strata may be of adifferent material having a level of hardness different from that ofrock salt.

According to one embodiment, an example of a suitable salt dome is onein which caverns are commonly created using solution mining. Such a saltdome is commonly used to store natural gas or petroleum products (e.g.,caverns 421, 422, 423, 424 of FIG. 4).

With reference to FIG. 5, a storage system according to one embodimentis shown. The power house 305 is installed at (or near) the top of theshaft 304 and a storage weight 302 is suspended for movement along thevertical dimension of the shaft. Portions of the shaft may be surroundedby overburden 500 and caprock 501. A primary portion of the shaft may besurrounded by the salt dome 502. Such a shaft can be constructed, forexample, using a shaft boring machine, with cuttings carried to thesurface by drilling mud. According to one embodiment, at least portionsof the shaft are lined with a reinforcing material such as, but notlimited to, concrete, steel or a similar material to minimize thelikelihood of collapse or ground intrusion.

At the locations of some salt domes, the large shaft depth achievableand the ease of shaft construction provide the potential for largestorage capacity per shaft constructed. For example, a shaft having across-sectional diameter of 10 meters and a depth of 6 kilometers wouldprovide sufficient space for a concrete storage mass of more than100,000 tonnes, thereby providing a storage capacity on the order ofthree gigawatt-hours.

Due to the relatively large cross-sectional diameter of some salt domes,salt domes can accommodate two or more systems (e.g., system 30)according to embodiments of the present invention. With reference toFIG. 6, a salt dome 600 accommodating multiple shafts 304, each shaftcorresponding to a power house 305, is shown. (Adjacent (or neighboring)shafts and power houses are spaced apart from each other by a suitabledistance.) For example, a salt dome having a cross-sectional diameter of2 kilometers has a cross-sectional area of about 3 square kilometers. Ifthe “footprint” of each power house 305 (which may provide sufficientaccess to the power house) occupies approximately 250 square meters, thesalt dome can accommodate a total of 12,000 power house/shaft pairings.If each of these pairings provides 25 megawatts of power for eighthours, or 200 megawatt-hours, the total capacity of the site would be300 gigawatts for 8 hours, or 2,400 gigawatt-hours.

According to one embodiment, a system is configured to lower and raisetwo or more weights. For example, the weights are lowered or raised by ahoist assembly individually (e.g., one at a time). With reference toFIG. 7, a group of storage weights 704 a, 704 b, 704 c, 704 d, 704 e,704 f, and 704 g are manipulated in the system. The individual weightsmay be coupled to hoist assembly 701 via hoist cable 703. According toone embodiment, the weights are generally equal in mass relative to eachother and generally similar in size and shape. According to anotherembodiment, the weights have different masses relative to each otherand/or have difference sizes and shapes. As explained previously, themasses of the weights may be chosen to provide the amount of energy thatis generated (or stored) when the weight is lowered (or raised) from (orto) the higher elevation.

At the higher elevation, the weights 704 b-704 g are supported by a rack702 located at (or near) the top of the shaft 704. An example of a rack702 will be described in more detail below with reference to FIG. 9. Atthe lower elevation, the weights may rest on each other and/or a base(e.g., base 806 of FIG. 8B) located at (or near) the bottom of the shaft704.

With reference to FIG. 8A, a top view of storage weight 804 a is shownaccording to one embodiment. According to one embodiment, the storageweight 804 a has a circular cross-section. According to otherembodiments, the storage weight has an oval, square, or rectangularcross-section. The weight 804 a may have a receptacle 805 forinterfacing with the hoist cable (e.g., hoist cable 703 of FIG. 7) tofacilitate raising and lowering of the weight 804 a along the shaft.According to one embodiment, the weight is constructed of concrete,reinforced concrete or another suitably dense material. According to oneembodiment, the grapple receptacle 805 is formed of a durable materialsuch as, but not limited to, steel.

With reference to FIG. 8B, a cross-sectional view of a stack of storageweights in the lowered configuration is shown according to oneembodiment. The weight 804 c is positioned to rest directly on base 806.Weights 804 b and 804 a are positioned to rest, respectively, on weight804 c and 804 b.

As previously described, at the higher elevation, the weights may besupported by a storage rack located at the top of the shaft. Withreference to FIG. 9, a cross-sectional view of a storage rack 900according to one embodiment is shown. The storage rack has a frame 901that is sized to be positioned inside a shaft (e.g., shaft 704 of FIG.7). The frame may include, for example, a cylindrical pipe-likestructure or other suitable structure forming one or more walls aroundthe periphery of the shaft (e.g., shaft 704), at least along a portionof the length of the shaft.

According to one embodiment, the frame 901 is configured to provide oneor more walls adjacent opposite edges of each of the weights. Accordingto one embodiment, the frame 901 includes latches 902 (e.g., latches 902a and 902 b) including retractable protruding members that arecontrollable to extend from and retract into the frame 901. The latches902 a and 902 b are configurable to hold weights in place, as desired.Latches 902 a are shown in an extended state to support storage weights904 a and 904 b. According to one embodiment, in the extended state, thelatches are configured to selectively engage one or more end surfacessuch as, but not limited to, bottom surfaces of the weights. Accordingto another embodiment, the latches are configured to selectively engageand extend into one or more recesses (such as, but not limited to,notches) on the weights. Latches 902 b are shown in a retracted state.However, the latches 902 b are extendable to receive a next weight thatis raised to the higher elevation. According to one embodiment, in theretracted state, the latches are configured to retract to positions thatdisengage the latches from the weights, such as, but not limited to,positions within recesses (such as, but not limited to, notches) on theframe 901.

As previously described, the latches are controllable to extend from andretract into the frame. According to one embodiment, the latches haveactuators that are controllable to selectively extend and retract thelatches. In a further embodiment, the actuators are manuallycontrollable via, for example, levers or switches that are capable ofbeing manually operated from a location accessible to a human operator.

According to another further embodiment, the actuators areelectronically controllable. The actuators are in communication withelectronic circuitry via, for example, one or more conductive orwireless links. Examples of electrically conductive links include, butare not limited to, electrical wires or cables. The control of theactuators by the electronic circuitry may be based on hardware and/orsoftware. For example, sensor devices detecting the presence of a weightat a certain position may trigger the actuator to extend thecorresponding latch(es) from the retracted position (see, for example,latch 902 b of FIG. 9) to the extended position (see, for example, latch902 a of FIG. 9). As another example, a software routine detecting thedemand for additional power at a certain time may trigger the actuatorto retract the corresponding latch(es) from the extended position to theretracted position such that the latched weight is freed from the rack.

Other control routines for controlling the timing of latch extending orretracting operations (for selectively holding or releasing weights) maybe provided, by suitable hardware and/or software and suitableprocessing electronics for processing the routines and providing controlsignals to latch actuators. Such control routines can be based, at leastin part, on the detection of the presence of a weight or the detectionof a demand for additional power (e.g., a demand exceeding a specifiedthreshold value) and/or other factors including, but not limited to,preset times of day, dates, environmental conditions, or manual input.

While the embodiment in FIG. 9 shows latches on one or more walls of theframe 901 and recesses or catch surfaces on the weights 904 a-b, inother embodiments, the retractable/protruding latches can be located onthe weights, and the receptacles can be positioned on the frame or rack.In yet other embodiments, the latches may be pivoting members, as willbe described in more detail below with respect to FIG. 15.

According to one embodiment, to store (or release) energy, the hoistassembly 701 raises (or lowers) the storage weights, one at a time, toposition the weights at the top (or the bottom) of the shaft. Withreference to FIGS. 10A, 10B and 10C, an example of a grapple interfaceis described in more detail. The grapple 1000 is positioned at the endof movable hoist cable 1010. The grapple has a central body 1000 a andone or more protruding members 1000 b. The grapple may also have aninner channel through which a connector, such as, but not limited to, acable or wire, may extend. In one embodiment, the protruding members1000 b are pivotally coupled to the central body 1000 a. In a furtherembodiment, the protruding members are pivotal between a first position(an open state) at which a portion of the member extends laterallybeyond the width of the central body and a second position (a closedstate) at which the member is aligned within (or within) the borders ofthe central body.

The grapple 1000 is controllable to be placed in the closed state or theopen state. According to one embodiment, the grapple is controlled totoggle between these two states in a manner similar to the manner inwhich the latches 902 of FIG. 9 are controlled, as described withreference to FIG. 9. For example, the protruding members 1000 b may haveactuators that are controllable to selectively pivot the protrudingmembers. In a further embodiment, the actuators are manuallycontrollable via, for example, a levers or a switch that is capable ofbeing manually operated.

According to further embodiments, the actuators are electronicallycontrollable. The actuators are in communication with electroniccircuitry via, for example, one or more conductive or wireless links.Examples of electrically conductive links include, but are not limitedto, electrical wires or cables. The control of the actuators by theelectronic circuitry may be based on hardware and/or software. Forexample, sensor devices detecting the presence of a weight around thecentral body 1000 a may trigger the actuator to pivot the protrudingmember from the closed position (see, for example, FIG. 10A) to the openposition (see, for example, FIG. 10B). As another example, a softwareroutine detecting the demand for additional power at a certain time andthe presence of a weight around the central body 1000 a may trigger theactuator to pivot the protruding member from the closed position to theopen position such that the engaged weight may be lowered. According toone embodiment, the controlling of the protruding member of the grappleis coordinated with the controlling of the latches (e.g., latches 902 ofFIG. 9) that lock the position of the weights, for example, such thatthe grapple is configured to be in the open position before the latchesthat engage a certain weight are retracted to free the weight.

As described previously with reference to latches 902 of FIG. 9, othercontrol routines for controlling the timing of grapple opening andclosing (for selectively holding or releasing weights) may be providedby suitable hardware and/or software and suitable processing electronicsfor processing the routines and providing control signals to grappleactuators.

A guide link 1020 extends through a channel in the grapple 1000 and atleast a portion of hoist cable 1010. In embodiments of the invention,the guide link 1020 may include, but is not limited to, a guide cable, aguide wire or a guide pipe. The position of the guide link 1020 may bestably fixed, for example, by securing one end of the guide link to afixed member (e.g., base 1040 of FIG. 10A). For ease of description, theguide link 1020 will be referred to as a guide cable.

With reference to FIG. 10A, the engagement of the grapple with a weight1030 that is to be raised is shown. In FIG. 10A, the grapple 1000 is inits closed state, and the weight 1030 is resting on base 1040. Guided bythe guide cable 1020, the closed grapple 1000 and the hoist cable 1010may be lowered past the grapple receptacle 1031 of the storage weight1030. Because the grapple 1000 is in its closed state, it may beextended past the grapple receptacle 1031 and into the channel 1032 ofthe weight 1030.

With reference to FIG. 10B, the grapple 1000 is shown in its open state.In this state, protrusions 1001 extend from the body of grapple 1000.The protrusions 1001 are configured to engage the grapple receptacle1031 of the weight 1030. As such, when the open grapple 1000 and thehoist cable 1010 are raised along the channel 1032, the protrusions 1001engage the grapple receptacle 1031, and the weight 1030 is capable ofbeing lifted by the hoist cable 1010 (see, for example, FIG. 10C). Thelifting of the weight is guided by the guide cable 1020. The guide cable1020 ensures that the storage weights are properly aligned with the base1040 (during lowering of the storage weights) and also directs theraising of the weights to the storage rack (e.g., rack 900 of FIG. 9).For example, the guide cable 1020 may enable grapple 1000 to quicklyre-engage storage weight 1030 when it is desired that storage weight1030 be raised and returned to the rack (e.g., rack 900 of FIG. 9).

As such, grapple 1000 may be used to individually raise weights alongthe shaft. In a similar manner, the grapple can individually engage theweights (e.g., via grapple receptacle 1001) such that the weights can beindividually lowered along the shaft. For example, at the higherelevation, the closed grapple is lowered past a grapple receptacle of aselected weight and is placed in the open state to engage the grapplereceptacle. When the weight is released from the rack (e.g., the latchessupporting the weight are retracted into the rack), the lowering of thehoist cable and the grapple will lower the weight along the shaft. Whenthe weight reaches the bottom of the shaft, the grapple 1000 is put inits closed state to disengage from the weight. The hoist cable 1010 andthe grapple 1000 may then be raised to retrieve another weight.

Distributing the mass of one weight over multiple weights may reduce thestrain imposed on devices such as the hoist and the hoist cable. Weightsof slightly more than 100 tonnes each, when lowered at a rate of 10meters per second, may provide 10 megawatts of output power. Using morethan one system (e.g., the system described with reference to FIG. 7) incooperation (or tandem) with each other can aid in providing a more evenlevel of output power or a more even level of storage availability withrespect to time.

According to one embodiment, a friction drive hoist system 110 isemployed to raise and lower the weights in a system employing multipleweights. With reference to FIG. 11A, hoist pulley 1101 is operativelycoupled with hoist pulleys 1102 and 1103. Pulley 1108 is alsooperatively coupled with hoist pulleys 1102 and 1103. Hoist pulleys 1102and 1103 are operative to raise and lower a respective set of weightsalong tracks 1104 and 1105. For raising the weights, one or more of thepulleys may be operatively coupled to a drive source (such as, but notlimited to, a motor) to receive a drive force for raising the weight.For example, hoist pulley 1101 may be operatively coupled with such adrive source. With reference to FIG. 11B, the drums of hoist pulleys1102 and 1103 rotate in counter directions to raise grapples 1106 and1107. According to one embodiment, the hoist system 110 uses grapplesfor example (but not limited to) grapples similar to grapple 1000, whichwas described with reference to FIGS. 10A, 10B and 10C. For example,when grapple 1106 is engaged with a weight for lowering the weight fromthe top of the shaft to the bottom of the shaft, the drum of hoistpulley 1103 is caused to rotate in a clockwise direction. Concurrently,the drum of hoist pulley 1102 is caused to rotate in a counter-clockwisedirection, thereby raising grapple 1107 towards the top of the shaft.

The manipulation of two grapples 1106 and 1107 by a single cable loop1109 may render the hoist system 110 more efficient. For example, whenone grapple (e.g., grapple 1106) is carrying a weight from the top ofthe shaft to the bottom, the other grapple (e.g., grapple 1107) will berising, empty, from the bottom of the shaft to the top. The firstgrapple releases its weight (e.g., on base 1110), and the second grappleengages a weight and transports it to the bottom of the shaft, and soon. Although only four weights are shown in FIG. 11A, other embodimentsof the system may accommodate less or more than four weights. Withreference to FIG. 11C, a cross-sectional view of the shaft is shown. Twoweights 1109 are positioned for movement along its respective track 1104and 1105.

According to certain embodiments, systems similar to those describedabove (e.g., system 20 of FIG. 2) are configured for use in an aquaticenvironment, such as but not limited to, a large body of water—e.g., anocean, sea, deep lake or the like.

With reference to FIG. 12, a side view of a sea-based system 120according to one embodiment is shown. The system includes a buoyantplatform 1210. According to an exemplary embodiment, the platform 1210is formed of one or more cylindrical flotation members (see, forexample, the members 1211 of the cross-sectional view of FIG. 12A).According to a further embodiment, the cylindrical members 1211 aregenerally hollow, water-tight, closed containers that contain a materialless dense than water (e.g., air) to increase the buoyancy of theplatform 1210. According to a further embodiment, the cylindricalmembers 1211 contain a material (e.g., low-density foam) to prevent themembers from filling with water and sinking in the event of a leak.According to yet another further embodiment, interior structuralreinforcement members (e.g., struts) may be positioned inside thecylindrical members to provide additional structural reinforcement.

In other embodiments, the members 1211 may take the form of othershapes, such as, but not limited to, that of polygonal boxes or ofspheres.

According to one embodiment, the walls of the cylindrical members areformed of steel or a suitably rigid and/or durable material. A platformformed by cylindrical members such as those described with reference toFIGS. 12 and 12A is known as a “spar” platform. According to alternativeembodiments, buoyant platforms may be formed according to other suitabledesigns.

With continued reference to FIG. 12, the platform 1210 supports a powerhouse 1200, for example, at one end of the platform. As described withrespect to earlier embodiments, the power house 1200 may include a hoist1201, a motor/generator and other related equipment. A ballast 1220 ispositioned, for example, at an opposite end of the platform 1210relative to the end at which the power house is located. As will bedescribed in more detail below, the ballast 1220 is for positioning thesystem 120 for operational use.

According to other embodiments, the power house 1200 (e.g., the hoist1201, motor/generator, and related equipment) may be positioned in theplatform (e.g., in a chamber inside the platform) to be closer to theballast 1220 such that the center of gravity of the system 120 islowered. As such, the system may be submerged deeper in the body ofwater, and may be rendered less susceptible to movement due to wind andwater currents. For example, according to one embodiment, the powerhouse 1200 may be positioned immediately above the ballast 1220. In anembodiment where the power house 1200 is housed in a chamber in theplatform 1210, the chamber may be pressurized and/or sealed to help keepwater from entering the chamber.

With reference to FIG. 12A, in the platform 1210, a generally verticalchannel or passage 1212 is provided generally at the center of theplatform. The channel may be defined by a member such as, but notlimited to, a cylindrical member such as a pipe or a shaft. The channel1212 extends through the platform 1210 to facilitate the raising andlowering of the hoist cable 1230, which is coupled with the hoist 1201.

At one end, the hoist cable (or wire, rope, belt, chain or the like)1230 is coupled with the hoist 1201. At the opposite end, the hoistcable 1230 coupled with storage weight 1240. As such, the storage weight1240 is suspended in the water by hoist cable 1230. According to oneembodiment, the storage weight 1240 is similar to storage weightsdescribed above with respect to other embodiments (e.g., storage weight303 of FIG. 3). For example, the storage weight 1240 may be constructedof concrete, reinforced concrete, steel, or some suitably densematerial.

According to one embodiment, the platform 1210 is moored to the floor1270 of the body of water to prevent the system 120 from drifting due towind or water currents. According to one embodiment, the platform 1210is moored to the floor 1270 via mooring lines 1250. According to oneembodiment, the mooring lines may be any suitable connection structuresuch as, but not limited to, cables, ropes, or chains securable to thefloor by stakes, anchors or the like. One or more electric transmissioncables 1260 may be provided to transport energy released by the system120. According to one embodiment, the transmission cables 1260 extendfrom the power house 1210 to the floor 1270, and from the floor to shorefor connection to a power grid (e.g., power grid 204 of FIG. 2).

In operation, the system of FIG. 12 operates similarly to systemsdescribed above with respect to other embodiments (e.g., system 300 ofFIG. 3). The raising of the storage weight 1240 using hoist 1201 storesenergy in the system 120 in the form of gravitational potential energy.The lowering of the storage weight 1240 releases the stored energy,generating power that may be carried by transmission cable 1260.

According to one embodiment, lowering the weight 1240 through water atmodest speeds minimizes (or at least reduces) drag losses. For example,a 10-meter diameter concrete sphere may have a mass of 1309 metric tonsand, correspondingly, may release over 6.3 megawatt-hours of energy whenit is lowered through 3000 meters of water. If the weight is lowered ata speed of 1 meter per second, energy is released at the rate of over7.5 megawatts over that period. As such, according to a modeled system,it is estimated that drag losses can amount to less than 0.3% of theenergy released. A weight having a shape computed to provide betterhydrodynamic performance than a sphere (e.g., a capsule-shaped weightwith rounded ends such as a weight having the shape of weight 1240) willreduce drag losses further.

As previously described with reference to FIG. 2, a weight of a systemmay be lowered (or raised) at two or more different speeds. As describedabove with reference to FIG. 3, in one embodiment, with reference toFIG. 12, a speed at which the weight 1240 is raised by hoist 1201 iscontrolled electronically. For example, according to one embodiment, amotor/generator for driving hoist 1201 is controlled by a controlcircuit coupled with the motor/generator to control the rate at whichhoist cable 1230 is drawn in by hoist 1201. According to anotherembodiment, such a control circuit may be coupled with the hoist 1201 tocontrol such a rate.

With continued reference to FIG. 12, in one embodiment, a speed at whichthe weight 1240 is lowered by hoist 1201 is controlled by configuring anoperating frequency of a generator (e.g., generator 200 of FIG. 2)coupled with the hoist. Configuring the operating frequency to be of acertain value correspondingly sets the speed at which the weight 1240 islowered. Alternatively, if such a generator is synchronous with a powergrid (e.g., power grid 204 of FIG. 2), the gear ratio of a gearbox maybe configured to control the speed at which the weight 1240 is lowered.For example, according to one embodiment, a gearbox may be coupledbetween the hoist 1201 and the generator (see, for example, FIG. 21).Configuring the gear ratio of such a gearbox to be of a certain valuecorrespondingly sets the speed at which the weight 1240 is lowered.

With continued reference to FIG. 12, in an alternative embodiment, aspeed at which the weight 1240 is lowered by hoist 1201 is controlled byor using a mechanical structure. For example, according to oneembodiment, a dampening structure (providing, for example, one or morelevels of dampening) is provided to control the rate at which hoistcable 1230 is drawn out from hoist 1201. Such a dampening structure mayinclude, but is not limited to, an adjustable clamp configurable toincrease the rotation resistance of the drum of hoist 1201. According toanother embodiment, the hoist 1201 includes a structure for setting sucha resistance (such as, but not limited, a screw that may be tightened orloosened). The dampening structure described above may be operablemanually (e.g., from a location accessible to a human operator) or by anelectronically controllable device such as an actuator.

Similar to the system of FIG. 7, a sea-based system according to oneembodiment may employ two or more storage weights. With reference toFIG. 13, the system 130 includes weights 1340 a, 1340 b, 1340 c, 1340 d,and 1340 e. Similar to the system of FIG. 7, the weights 1340 a to 1340e may be individually raised and lowered. When raised, the weights maybe supported by a rack 1350 suspended from the platform 1310. Accordingto one embodiment, the rack 1350 is similar to racks such as rack 900,which was described with reference to FIG. 9. To release energy, thehoist 1301 lowers the storage weights, one at a time, and rests them ona base 1380 placed on the floor of the body of water. As will bedescribed in more detail with respect to FIG. 15, according to oneembodiment, the weights may be supported by storage rack 1350 usinglatches. As will be described in more detail with respect to FIG. 16,according to one embodiment, a grapple 1600 is used to engage eachstorage weight 1340 a, 1340 b, 1340 c, 1340 d, 1340 e for raising andlowering the weight through the water.

According to one embodiment, a guide cable 1370 (which may be similar,for example, to guide cable 1020 of FIGS. 10A, 10B and 10C) may help toensure that the storage weights 1340 a to 1340 e are properly alignedwith the rest base 1380 and enables the grapple 1600 to quicklyre-engage with a weight to return the weight to the rack 1350. Accordingto one embodiment, two or more systems such as the system of FIG. 13 areused in cooperation (or in tandem) to provide a more even level ofoutput power and/or a more even level of storage availability.

With reference to FIG. 14A, a top view of a storage weight 1440according to one embodiment is shown. According to one embodiment, theweight 1440 is configured for improved underwater performance. Grapplereceptacle 1441 is provided to engage with the grapple (e.g., grapple1600 of FIG. 13). In addition, the grapple receptacle 1441 defines (atleast in part) the channel 1444 through which the grapple (e.g., grapple1600 of FIG. 13), the hoist cable, and the guide cable (e.g., cable 1370of FIG. 13) may extend. The weight 1440 may be shaped such that most (ormuch) of its mass in located at its periphery. In an embodiment wherethe weight has a circular cross-section, most (or much) of its weight islocated at its rim 1442. As such, the weight is better suited todecrease drag. In other embodiments, the peripheral portion of theweight 1440 may have other suitable shapes. According to one embodiment,the density of the material forming the rim 1442 may be greater than thedensity of the material forming the interior portion 1443 of the weight.According to another embodiment, the interior portion 1443 is open (orhollow). The rim 1442 (and potentially other portions of the weight) maybe constructed of reinforced concrete or a suitably strong material suchthat the weight is better capable of withstanding water pressure whenthe weight is submerged significantly below the water surface.

With reference to FIG. 14B, a side cross-sectional view of the weights1440 b, 1440 c, 1440 d and 1440 e is shown. According to one embodiment,the weights are configured to rest on base 1480. According to oneembodiment, each of the weights is configured such that its center ofgravity is located below the grapple receptacle 1441 to improve thestability of the weight as it is lowered or raised through water.According to a further embodiment, the weight 1440 is streamlined tosmooth the surface area of its outer surfaces (such as, but not limitedto, the surfaces directly pushing against water when the weight islowered or raised) to minimize (or reduce) fluid drag.

An embodiment of the storage rack is shown in FIG. 15. According to oneembodiment, the rack 150 has a frame 1560 that is configured to provideone or more walls adjacent opposite ends of each of the weights. Theframe 1560 may include retractable (or pivotable) latches 1562 (e.g.,latches 1562 a and 902 b) that are controllable to extend (or pivot)from and retract into (or pivot back to) the frame 1560.

In one embodiment, the latches 1562 are pivotally coupled to the frame.In a further embodiment, the latches are pivotal between a firstposition (an extended state) at which a portion of the latch extendslaterally beyond the width of the frame and a second position (aretracted state) at which the latch is generally aligned with or withinthe borders of the frame.

The latches are controllable to be placed in the extended state or theretracted state. According to one embodiment, the control of the latchesis similar to that described with respect to latches 902 of FIG. 9. Forexample, the latches 1562 may have actuators that are controllable toselectively pivot the latch. In a further embodiment, the actuators aremanually controllable via, for example, a levers or a switch that iscapable of being manually operated, for example, as described above withrespect to FIG. 9. According to another further embodiment, theactuators are electronically controllable in a manner similar to theelectronic control of the actuators of latches 902 of FIG. 9.

The latches 1562 a and 1562 b are configured to support weights on thestorage rack 150. Latches 1562 a are shown in an extended state tosupport storage weight 1540. According to one embodiment, in theextended state, the latches engage a surface feature (such as, but notlimited to, a bottom surface) of the weight. Latches 1562 b are shown ina retracted state. However, the latches 1562 b are extendable to supporta next weight that is raised.

According to another embodiment, the latches 1562 are configured toextend from and retract into frame 1560, similar to the configuration oflatches 902, which were described with reference to FIG. 9.

The operation of grapple 1600 is now described in more detail withreference to FIGS. 16A, 16B and 16C. In one embodiment, the grapple 1600is similar to grapple 1000, which was described with reference to FIGS.10A, 10B and 10C. For example, similar to the grapple 1000, the grapple1600 has a central body 1600 a and one or more protruding members 1600b. Further, the grapple 1600 may also have an inner channel throughwhich a connector such as, but not limited to, a cable or wire mayextend. Further, in one embodiment, the protruding members 1600 b arepivotally coupled to the central body 1600 a. In a further embodiment,the protruding members are pivotal between a first position (an openstate) at which a portion of the member extends laterally beyond thewidth of the central body and a second position (a closed state) atwhich the member is generally aligned with or within the borders of thecentral body.

According to one embodiment, the operation of the grapple 1600 issimilar to the operation previously described with reference to grapple1000 of FIGS. 10A, 10B and 10C. The grapple 1600 may be positioned atthe end of hoist cable 1661. The grapple 1600 is configurable to beplaced in a closed state or an open state in a manner similar to thatdescribed with respect to grapple 1000 of FIGS. 10A, 10B and 10C. Inaddition, in one embodiment, the control of the state of the grapple1600 and the control of the state of the latches (e.g., latches 1562 ofFIG. 15) are coordinated in a manner similar to that described withrespect to latches 902 and grapple 1000. Guide cable 1670 extendsthrough a channel in the grapple 1600 and at least a portion of hoistcable 1661. The position of the guide cable 1670 may be stably fixed bysecuring one end of the guide cable to base 1680.

With reference to FIG. 16A, the engagement of a weight that is beinglowered is shown. The grapple 1600 is in its open state. In this state,protrusions 1601 extend from the body of grapple 1600. The protrusions1601 are configured to engage the grapple receptacle 1641 of the weight1640. As such, when the grapple 1600 is opened, the protrusions 1601engage the grapple receptacle 1641, and the weight 1640 may be loweredwith the hoist cable 1661. The lowering of the weight 1640 is guided bythe guide cable 1670. The guide cable 1670 may ensure that the storageweight is properly aligned with the rest base 1680 and also may enablethe grapple 1600 to more quickly re-engage with the weight when it isdesired that the weight be returned to the rack (e.g., rack 15 of FIG.15). With reference to FIG. 16B, the weight 1640 is lowered to rest onbase 1680.

With reference to FIG. 16C, the grapple 1600 is configured to releasethe weight 1640 so that the grapple 1600 and hoist cable 1661 can beraised to retrieve a next weight. The grapple 1600 is in a closedposition. Because the grapple 1000 is in its closed state, it maydisengage with the grapple receptacle 1641 of the weight 1640. As such,the grapple 1600 and the hoist cable 1661 may be raised to leave theweight 1640 remaining at its rest position (e.g., on base 1680).

As such, grapple 1600 may be used to individually lower weights throughwater. It is understood that, in a similar manner, the grapple may beused to individually raise weights through the water. As previouslydescribed with respect to FIG. 15, when a weight is raised to thestorage rack, it may be supported by the rack (e.g., using the latchesshown in FIG. 15).

According to one embodiment, a system (e.g., the system of FIG. 13) maybe configured to by powered by renewable energy as well as moreconventional sources such as hydrocarbons to raise weights at desiredtimes.

With reference to FIG. 17, a system 170 may include a wind turbineenergy generator 1700. The generator 1700 is for generating energy fordriving the hoist 1720 to raise weight 1720 through the water. As such,wind energy captured by the wind turbine energy generator 1700 may bestored in the system 170 as gravitational potential energy. The storedenergy may be released at a later time (e.g., when demand for power isgreater).

Oceanic sites, including sites located relatively distant from land, canbe appropriate for a wind turbine such as wind turbine 1700. If the siteis located relatively distant from land, the wind turbine may be beyondvisible and/or audible range from land. Therefore, observers on landlikely will tend not to view the turbine as an “eyesore” and/or as asignificant source of noise pollution. Further, sites can be chosen tobe located away from known or likely routes used by migrating birds.Therefore, it is less likely that the operation of the turbine willaffect wildlife. Such sites can be selected for minimizing environmentalimpact.

Furthermore, because the system of FIG. 17 provides a surface (e.g., asurface of the platform structure 1730 such as a surface of thepowerhouse 1710) for supporting the turbine 1700, a separate platformfor supporting the wind turbine is not required, thereby reducing thecosts typically associated with installing a wind turbine offshore. Theplatform 1730 may be configured to be sufficiently buoyant to supportthe weight of the turbine 1700 such that the blades of the turbineremain above water during operation. A ballast 1740 at the bottom of theplatform 1730 helps maintain the system 170 in an operational position.

As previously described, at least part of the energy captured by thewind turbine 1700 can be stored and subsequently released at a moresuitable time in order to produce a more even level of output power overtime. As such, the wind turbine is thereby converted from a relativelyintermittent power source that might provide power of only a relativelylow value (e.g., power that is captured during off-peak periods) to adispatchable power source that provides power of a relatively highervalue (e.g., power that is provided during peak periods). In otherwords, wind energy that is captured during periods of low power demand,such as late at night, may be stored in the system. The stored energymay be released (e.g., to a grid) during periods of high power demand,when power is much more valuable.

According to one embodiment, a system such as the system of FIG. 17 maybe configured for convenient transport and installation at sea. FIGS.18A and 18B respectively show top and side views of a system accordingto such an embodiment. As will described in more detail below, thesystem 180 may be positioned on its side (e.g., in the positionillustrated in FIG. 18B) for example, for transportation, storage, orservicing, on land and in dry dock. The system 180 may be configured ina manner such that heavy equipment such as cranes may not be required tomove the system.

With reference to FIG. 18, the system 180 includes a spar 1850,flotation devices 1830, a wind turbine 1890 including tower 1810, towersupports 1800, slidable piston 1880 and ballast tank 1840. According toone embodiment, the spar 1850 has a cylinder 1860 sized to receive thetower 1810. According to a further embodiment, the spar 1850 is similarin structure to spar 1210, which was described with reference to FIG.12. For example, the spar 1850 may include one or more cylindricalflotation members that may be similar to members 1211, which also weredescribed with reference to FIG. 12. Flotation devices 1830 may also besimilar to members 1211. The wind turbine 1890 includes blades and tower1810 which supports the blades of the turbine. According to oneembodiment, the flotation devices 1880 are similar in structure tomembers 1211. The tower supports may include a malleable structure thatmay be configured to have a shape conforming to an adjacent object(e.g., the tower 1810).

According to one embodiment, the system 180 is configured in a mannersuch that the wind turbine tower 1810 is retracted into a cylinder(e.g., a central cylinder) 1860 of the spar 1850. One end of the tower1810 is coupled with a slidable piston 1880. In one embodiment, towersupports 1800 may be removably provided at the entrance to the cylinder1860 to support the tower 1810 (e.g., to minimize wobbling duringtransport). In one embodiment, a ballast tank 1840 is located at theopposite end of the spar 1850. In a further embodiment, stabilizationfloats 1830 are removably attached to each side of the spar 1850 tostabilize the platform during transport. With continued reference toFIG. 18A, the illustrated system is ready to be transported (e.g.,towed) to an installation site (e.g., an installation site locatedoffshore).

With reference to FIG. 18B, the illustrated system is at the aquaticinstallation site and ready to be installed at the site.

A procedure to install the platform for operation will now be describedwith reference to FIGS. 19A, 19B and 19C. With reference to FIG. 19A,the ballast tank 1840 may be configured to take in water 1900. As theballast tank 1840 continues to take in water, the center of gravity ofthe spar 1850 changes accordingly. The change in the center of gravitycauses the ballasted end of the spar 1850 to sink deeper into the water(see, for example, FIGS. 19A and 19B). The ballast tank 1840 isconfigured to take in a sufficient amount of water such that theequilibrium position of the spar is a standing position (see, forexample, FIG. 19C). When the spar 1850 stands upright, as shown in FIG.19C, it may then be positioned in the desired location and then mooredto the floor of the body of water so that its position is fixed. One ormore storage weights may be coupled for operation with the system suchthat gravitational potential energy may be stored in the system. Forexample, one or more storage weights may be coupled according to aconfiguration similar to that illustrated in FIG. 17.

The procedure to install the platform for operation will now be furtherdescribed with reference to FIGS. 20A, 20B and 20C. As previouslydescribed, the tower 1810 is positioned in a cylinder 1860 in the centerof the spar 1850, and the lower end of tower 1810 is coupled with aslidable piston 1880. The piston 1880 is caused to slide upward, therebypushing the tower 1810 in an upward direction (see, for example, FIGS.20B and 20C). According to one embodiment, the piston 1880 is caused toslide upward when air is pumped into the cylinder 1860, at the locationbelow the piston 1880 (between the piston 1880 and the ballast tank1840). A suitable air inlet port (not shown) may be provided on the sparfor connection to a pressurized air source (not shown). The sliding ofthe piston 1880 may be continued until the tower 1810 reaches its fullyextended position. The air inlet may be sealed after the piston 1880 isslid into its extended position. According to one embodiment, the tower1810 reaches its fully extended position when the piston 1880 reachesthe end of the spar 1850 (see, for example, FIG. 20C). The tower 1810may be bolted or otherwise suitably fastened in place.

Under known techniques, a wind turbine tower, which can be over 100meters tall, requires extremely tall and expensive cranes to raise thetower and hoist the nacelle and turbine blades of the tower. This wouldbe especially difficult and expensive in deep ocean water, where thewaves can be large and the winds can be strong. In contrast, theprocedure described with reference to FIGS. 19A, 19B, 19C, 20A, 20B and20C may not require such equipment, thereby saving both time andexpense. Furthermore, certain steps in the procedure may be reversible.For example, the tower 1810 may be lowered (e.g., retracted) back intothe cylinder 1860—e.g., to place the nacelle closer to the water wherereplacement of faulty components can be accomplished more easily.

As previously described, wind turbines with energy storage systems, suchas those disclosed herein with reference to certain embodiments, mayprovide significant cost savings. Wind power can be used to turn a rotorin a motor/generator to generate electrical power to be used to raiseone or more weights. Alternatively, with reference to FIG. 21, a windturbine 2110 is directly mechanically coupled with a shaft storagesystem (e.g., a system similar to the storage system of FIG. 13),allowing direct use of wind power to hoist the storage weight 2130 viahoist 2120. That is, the rotation of the rotor of the turbine 2110causes one or more gears of gearbox 2140 to rotate. The rotation of thegears causes the drum of hoist 2120 to rotate, thereby raising weight2130. The coupling of a generator between the turbine 2110 and the hoist2120 may not be required, thereby saving costs and rendering the designof the system 210 more simple and less complex. As previously described,such a system facilitates the release of captured wind energy (e.g., toa power grid) on an as-needed basis, rather than only when the windblows. As a result, the value of the wind energy may be substantiallyincreased.

A schematic representation of a combined system 220 according to anotherembodiment is shown in FIG. 22. In the system 220, the wind turbine 2200drives a hydraulic pump 2210, which pumps hydraulic fluid (e.g., highpressure hydraulic fluid) through a pressure hose 2220 to a hydraulicmotor 2230. The hydraulic motor 2230 drives hoist 2240 to lift thestorage weight 2250. According to one embodiment, when the storageweight 2250 is lowered, the hoist 2240 is rotated to rotate one or moregears of the gearbox 2270. The rotation of the gears is converted toelectrical power by generator 2260. According to a further embodiment,two or more hydraulic lines such as pressure hose 2220 may be coupledtogether to drive hydraulic motor 2230, thereby facilitating the drivingof hoist 2240 using the output of more than one wind turbine.

Another embodiment of the invention will now be described with referenceto FIGS. 23A and 23B. The system 230 in FIGS. 23A and 23B includes ashaft structure 2320 including, for example, but not limited to, agenerally cylindrical pipe made of a suitably rigid material, such as,but not limited to, metal, plastic, a composite material or the like.The pipe has a central channel in which a weight 2310 is supported formovement between a first position (shown in FIG. 23B) and a secondposition (shown in FIG. 23A). The system 230 also includes a pump 2340,a pipeline 2360 and a motor/generator 2350. According to one embodiment,the pipeline includes, but is not limited to, a tube-like structure madeof a suitably rigid material, such as, but not limited to, metal,plastic, a composite material or the like. The weight 2310 is sized tomove within the channel of the shaft structure 2320. In one embodiment,the weight is made of a suitably dense material such as, but not limitedto, concrete, steel or the like. The pressure seals 2320 are sized to atleast span a gap between the weight 2310 and the inner periphery ofshaft structure 2320 to form a water-tight seal therebetween. Accordingto one embodiment, the pressure seals are formed of a durable, flexiblematerial such as, but not limited to, plastic, rubber or the like.

The operation of system 2300 is similar to that of the system of FIG. 2in that the system 2300 also stores gravitational potential energy usinga storage weight that is caused to be elevated and lowered. With regardsto the embodiment of FIG. 23A, weight 2310 is positioned in the channelof shaft structure 2320 that facilitates the inflow and outflow of ahydraulic fluid. For ease of description, the shaft structure 2320 willbe referred to as a storage pipe. According to one embodiment, thehydraulic fluid is water.

With continued reference to FIG. 23A, the weight 2310 is sized to beslidably positioned within the pipe 2320. According to one embodiment,the weight 2310 is sized to narrowly but slidably fit within theconfines of pipe 2320. As such, the size of the weight can be maximizedto increase the amount of gravitational potential energy that can becaptured by the weight, without significantly affecting the freedom ofthe weight to move within the pipe 2320. According to a furtherembodiment, a pressure seal 2330 may be provided on the weight 2310 toprevent the hydraulic fluid from flowing past the seal 2330. As shown inFIG. 23A, the seal 2330 is disposed at the lower end 2310 a of theweight 2310. In other embodiments, the seal 2330 may be disposed at theupper end 2310 b of the weight 2310, or between the lower end 2310 a andthe upper end 2310 b.

With continued reference to FIG. 23A, a pump (or pump-turbine) 2340 isconnected by pipeline 2360 to the top and bottom of the pipe 2320, andis connected through a driveshaft to an electric motor/generator 2350.As shown in FIG. 23A, the pump 2340 is positioned near the upper end ofthe pipe 2320. In other embodiments, the pump 2340 is positioned nearthe lower end of the pipe 2320, or between the upper and lower ends. Themotor/generator 2350 is also connected to an external source of electricpower, such as the power grid 2380, for example, via substation 2370.

In operation, when electric power is provided by the external source2380 to the motor/generator 2350, the motor/generator 2350 drives thepump 2340 to increase the pressure of the hydraulic fluid along thedirection indicated in the arrows of FIG. 23A in pipeline 2360. As aresult, pressure in the fluid below weight 2310 is increased, forcingthe weight 2310 to rise toward the upper end of shaft 2320. As such,gravitational potential energy is stored in the system 230 (see, forexample, the configuration of FIG. 23B). According to one embodiment,when the weight 2310 reaches an elevated position (such as, but notlimited to, the position of FIG. 23B), latches, as described above,valves in pipe 2360 or in pipe 2360, a lock on the pump turbine oranother suitable structure are operated to maintain the pressure of thehydraulic fluid supporting the weight 2310. For example, similar to thelatches described previously, such structures may be operated manuallyand/or electronically.

According to other embodiments, air or a gaseous material may be usedrather than (or in combination with) a liquid in the shaft 2320 to pushweight 2310 in an upwards direction. According to these embodiments, anair compressor may be used in place of (or in addition to) the pump 2340to increase the pressure of the air, thereby elevating the weight 2310.

The release of energy stored in the system 230 will now be described inmore detail with reference to FIG. 23B. In one embodiment, themaintenance structures (e.g., latches, valves, or locks) are operated torelease the pressure of the hydraulic fluid supporting the weight 2310.When the weight 2310 is allowed to drop towards the lower end of theshaft 2320, the mass of the weight forces the liquid to flow out throughthe pipe 2320 and through the pipeline 2360 in the direction of thearrows indicated in FIG. 23B in the pipeline 2360. The flow of theliquid drives the pump 2340, which causes the generator 2350 to produceelectric power to be transmitted, for example, to the power grid 2380.In embodiments employing a gaseous substance (such as, but not limitedto, air) in place of a liquid, the falling weight 2310 causes the airbeneath the weight 2310 and in the pipeline 2360 to pressurize. Thepressurized air drives the pump/turbine 2340, which causes the generator2350 to produce electric energy.

According to an embodiment employing a liquid as the pressurizedmaterial, the liquid is selected/configured to reduce operational energylosses that may be incurred in the system. For example, in oneembodiment, the composition of the liquid is modified by addingpolyethylene-oxide or a similar substance to the liquid (e.g., water) inorder to decrease turbulence that may be experienced by the movingweight 2310 and to decrease the amount of friction caused by the slidingof the pressure seal 2330 against the pipe 2320. According to yetanother embodiment, a liquid other than water can be used. For example,petroleum may be used because it has a lower density than water.Therefore, the use of petroleum may increase the negative buoyancy andeffective storage capacity afforded by weight 2310 on a cubic-meterbasis. In addition, the replacement of water with petroleum woulddecrease the friction caused by the sliding of pressure seal 2330against the pipe 2320.

As previously described with reference to FIG. 2, a weight of a systemmay be lowered (or raised) at two or more different speeds. Withreference to FIG. 23A, in one embodiment, a speed at which the weight2310 is raised by the fluid is controlled electronically. For example,according to one embodiment, the motor/generator 2350 for drivingpump-turbine 2340 is controlled by a control circuit coupled with themotor/generator to control the level of fluid pressure that is produced.According to another embodiment, such a control circuit may be coupledwith the pump-turbine 2340 to control such a rate.

With continued reference to FIG. 23A, in one embodiment, a speed atwhich the weight 2310 is lowered along pipe 2320 is controlled byconfiguring an operating frequency of the generator 2350. Configuringthe operating frequency to be of a certain value correspondingly setsthe speed at which the weight 2310 is lowered. Alternatively, if thegenerator 2350 is synchronous with the power grid 2380, the gear ratioof a gearbox may be configured to control the speed at which the weight2310 is lowered. For example, according to one embodiment, a gearbox maybe coupled between the pump-turbine 2340 and the generator 2350 (similarto the configuration illustrated in FIG. 21). Configuring the gear ratioof such a gearbox to be of a certain value correspondingly sets thespeed at which the weight 2310 is lowered.

With continued reference to FIG. 23A, in an alternative embodiment, aspeed at which the weight 2310 is lowered along pipe 2320 is controlledby or using a mechanical structure. For example, according to oneembodiment, a dampening structure (providing, for example, one or morelevels of dampening) is provided to control the rate at which the fluidis forced out from pipe 2320 and into pipe 2360. Such a dampeningstructure may include, but is not limited to, a valve controlling suchinflow into pipe 2360. According to another embodiment, the pump-turbineincludes a structure for setting a rate of inflow from the pipe 2360 andto the pump-turbine. The dampening structure described above may beoperable manually (e.g., from a location accessible to a human operator)or by an electronically controllable device such as, but not limited to,a valve actuator.

According to another embodiment (similar to the respective embodimentsof FIGS. 7 and 13), multiple weights are utilized. In some instances,pumps (or pump-turbines) such as pump 2340 of FIG. 23A may accommodateonly up to a certain level of water pressure or “head.” Because thelevel of water pressure produced by a weight (e.g., the weight 2310 ofFIG. 23A) is determined by the density and height of the weight, asufficiently large and dense weight may potentially produce more waterpressure than the pump can comfortably handle. By using multipleweights, each of which is sized to produce a level of water pressurethat can be accommodated by the pump, incremental increases in waterpressure can be kept within comfortable levels.

In the embodiment illustrated in FIGS. 23A and 23B, one pipe 2320 andone pipe 2360 are shown. In other embodiments, a parallel configurationof two or more pipes similar to pipe 2320 (each having a weight similarto weight 2310 contained therein) may be coupled between pump-turbine2340 and pipe 2360. In other embodiments, a parallel configuration oftwo or more pipes similar to pipe 2360 may be coupled between pipe 2320and pump-turbine 2340. In yet other embodiments, a parallelconfiguration of two or more pipes similar to pipe 2320 (each having aweight similar to weight 2310 contained therein) may be coupled betweenpump-turbine 2340 and a parallel configuration of two or more pipessimilar to pipe 2360. The operation of the embodiments described in thisparagraph may be similar to the operation previously described withreference to FIGS. 23A and 23B.

With reference to FIG. 24, a system employing multiple weights is shown.The system 240 includes motor/generator 2450, pump-turbine 2440, pipe2420, return pipe 2460, and pressure seals 2330. In one embodiment, oneor more of these structures is similar to corresponding structure(s) inthe system of FIG. 23. The system 240 also includes a plurality ofweights 2410 a, 2410 b, 2410 c, 2410 d and 2410 e. As described withother weights in this disclosure, the weights 2410 a-e may be formed ofa suitably dense material (e.g., steel, concrete, or the like). In oneembodiment, each of the weights includes a valve 2412. Each of theweights 2410 a, 2410 b, 2410 c, 2410 d and 2410 e defines an innerchannel 2411 through which a liquid substance such as, but not limitedto, water may pass. According to one embodiment, the weights 2410 a-2410e may be supported by a storage rack (not shown) located at the top ofthe pipe 2420 and similar to the rack 900 described with reference toFIG. 9. In addition, such a rack may include latches (e.g., latchessimilar to latches 902, which were described with reference to FIG. 9)that are configurable to hold the weights in place on the rack.

In conjunction with latches similar to the latches 902 of FIG. 9, thevalves 2412 are configurable to position the weights, as desired. Valves2412 of weights 2410 a-2410 d are shown in an open state. According toone embodiment, in the open state, the valves have been configured toretract (or pivot) to open the inner channel 2411 at one end (e.g., thebottom end of the channel) such that liquid can enter the channel atthat end. As such, the corresponding weights are not configured forcontrolled movement along pipe 2420. Valve 2412 of weight 2410 e isshown in a closed state. According to one embodiment, in the closedstate, the valve has been configured to extend (or pivot) to close offthe inner channel 2411 at one end (e.g., the bottom end of the channel)such that liquid can not enter the channel at that end. Similar to thecontrol of the protruding members of the grapple 1000, as described withreference to FIG. 10, the valves 2412 are controllable to be placed inthe open or closed state. According to one embodiment, the valves haveactuators that, in a further embodiment, are manually controllable orelectronically controllable.

As described above, each of the weights may include an operable valve2412, which (in its open state) provides entry of the liquid into theinner volume 2411. When the valve 2412 is closed, the valve 2412 impedesentry of the liquid into the inner volume. The storage of energy and theaccompanying release of stored energy in the system of FIG. 24 may beconducted in a manner similar to that described with reference to FIGS.23A and 23B.

With reference to FIG. 24, during both energy-storage and energy-releasephases of operation, the valve 2412 in the weight (or weights) that isselected to be raised (or lowered) in the shaft 2420 is placed in itsclosed state (see, for example, the valve 2412 of weight 2410 e in FIG.24, which is in a closed state. As a result, weight 2410 e moves in adownward direction along pipe 2420, thereby incrementally increasing thepressure of the liquid delivered to pump-turbine 2440.

Also, during both energy-storage and energy-release phases of operation,the valve 2412 in the weight (or weights) that is selected to remainstationary is placed in its open state (see, for example, the valve 2412of weight 2410 a in FIG. 24). As a result, the position of weight 2410 ain pipe 2420 remains generally stable.

In embodiments described above, liquid pressure is produced underneath abody (e.g., weight 2310 of FIG. 23A) that is formed of a material thathas a density higher than that of the liquid flowing in the pipe. Inaddition, liquid pressure may be produced above a body—e.g., a bodyformed of a material that has a density that is less than that of theliquid flowing in the pipe. Such pressure can be formed in the system250, which will now be described with reference to FIG. 25. The systemincludes motor/generator 2550, pump-turbine 2540, weight 2510, pressureseals 2530 and pipe 2520. In one embodiment, one or more of thesestructures is similar to corresponding structure(s) in the system ofFIG. 23. The system also includes shaft structure 2560. The shaft 2560includes, for example, but not limited to, a generally cylindrical pipemade of a suitable rigid material, such as, but not limited to metal,plastic, a composite material or the like. The shaft 2560 has a centralchannel in which a vessel 2570 is supported for movement between a firstposition (shown in FIG. 25) and a second position at an upper end ofpipe 2560 (not shown). The vessel 2570 may have a shape of a capsule,cylinder, sphere, a box, or other shapes.

According to one embodiment, the vessel 2570 is a generally hollow,water-tight, closed container that contains a material less dense thanthe pressurizing liquid (e.g., air). According to one embodiment, thevessel 2570 is an air vessel, and air pressure within the vessel 2570may be configured to offset the external pressure of the liquid toprevent the vessel 2570 from collapsing. Pressure seals 2580 arepositioned on vessel 2570. Similar in function to the seals 2330 of FIG.23, the pressure seals 2580 of one embodiment are sized to at leastcover a gap between the vessel 2570 and the inner periphery of pipe 2560to form a water-tight seal therebetween.

With reference to FIG. 25, to release stored energy, a systemfacilitates the downward movement of weight 2510, which, similar toweight 2310 of FIG. 23A, is composed of a material that is more densethan the liquid beneath the weight 2510. The pressurizing force causedby the downward movement of weight 2510 along shaft 2520 may beaugmented by the pressurizing force caused by the upward movement ofbuoyant vessel 2570 along shaft 2560. The vessel 2570 contains amaterial that is less dense that the liquid flowing in the shafts 2520and 2560.

In an alternative embodiment, the system employs the buoyant vessel 2570but not the weight 2510 in the storage of energy and the release of thestored energy. Similar to embodiments previously described, the vessel2570 of this alternative embodiment contains a material having a lowerdensity than the surrounding liquid. Energy is stored when the turbineincreases the pressure of the fluid along a direction opposite to thearrows indicated in FIG. 23A in shaft 2540. As a result, pressure in thefluid above vessel 2530 is increased, pushing the vessel 2530 toward thelower end of shaft 2540 As such, energy is stored in the system 250(see, for example, the configuration of FIG. 25).

With reference to FIG. 26, another embodiment is shown. Features of thisembodiment include an integrated structure that may be configuredrelatively compactly. In this embodiment, a system 260 includesmotor/generator 2650, pump-turbine 2640, a return pipe 2660 and pressureseals 2630. In one embodiment, one or more of these structures issimilar to corresponding structure(s) in the system of FIG. 23. Thesystem 260 also includes a pipe 2620. The storage pipe 2620 includes,without limitation, a generally cylindrical pipe made of a suitablyrigid material such as, but not limited to, metal, plastic, a compositematerial or the like. The cylindrical pipe of the storage pipe 2620defines an inner channel through which at least a portion of the returnpipe 2660 extends. In one embodiment, the weight 2610 is sized to movewithin the pipe 2620, and, as such, has a shape generally conformingwith an inner volume of the pipe 2620. According to one embodiment,sliding pressure seals 2630 are positioned on the weight 2610 to atleast span a gap between the weight 2610 and the storage pipe 2620. Theseals 2630 prevent pressurized fluid from flowing past the seal.

In the configuration illustrated in FIG. 26, energy is released as theweight 2610 moves in a downward direction along the pipe 2620. The massof the weight 2610 forces the liquid to flow out through the pipe 2620and through the pipe 2660 in the direction of the arrows indicated inFIG. 26 in the pipe 2660. The flow of the liquid drives the pump 2640,which causes the motor/generator 2650 to produce electric power to betransmitted, for example, to a power grid.

According to a further embodiment, pressure tank 2670 is provided at oneend of the storage pipe 2620. The pressure tank 2670 may containcompressed air or a suitable gas. As such, the pressure tank 2670 allowsthe absolute pressure on the turbine output to be increased, therebypreventing cavitation and the resulting damage to turbine components.

According to one embodiment, wind energy may be used to drive systemsincluding systems such as the system 260 of FIG. 26. With reference toFIG. 27, a schematic representation of an embodiment of a wind-poweredsystem 270 is shown. According to this embodiment, the wind turbine 2700drives a hydraulic pump 2770 to pump hydraulic fluid (e.g., water)through a pressure hose 2780 and to return pipe 2760. The pressure ofthe water forces weight 2710 to move up along storage pipe 2720. The useof hydraulic pump 2770 may help eliminate the efficiency lossesassociated with using an electric pump (e.g., the efficiency lossesincurred by converting wind energy to electricity (for operating theelectric pump) and then converting the electricity back to mechanicalenergy (in the electric pump)). Further, fluid pressure provided by thewind turbine 2700 to pump-turbine 2740 (via pressure hose 2780) can becombined with fluid pressure provided from the downwardly-moving storageweight 2710 to pump-turbine 2740 (via return pipe 2760) to drive thepump-turbine, thereby spinning the motor/generator 2750 and providingelectricity, for example, to a power grid. This helps to eliminates theneed for a generator directly coupled to the wind turbine tower. Becausesuch a generator may be heavy and/or expensive, eliminating the need forsuch a generator decreases the structural requirements and/or costs ofthe system.

According to another embodiment, with reference to FIG. 28, a system 280similar to the system 260 of FIG. 26 can be configured for installationin an aquatic site. According to one embodiment, the storage pipe 2820may be configured to rest on the floor of the aquatic body (e.g., anocean). Guy lines 2890 (which, according to one embodiment, are similarto mooring lines 1250 of FIG. 12) serve to anchor the system to thefloor and aid in maintaining the system in a generally verticalorientation. According to a further embodiment, one or more buoyancychambers 2892 are provided at (or near) the upper end of the system toaid in maintaining the generally vertical orientation of the system.According to one embodiment, the buoyancy chambers 2892 are floatablemembers that are generally hollow and that contain a material having adensity less than that of water. According to one embodiment, thebuoyancy chamber 2892 is formed of a rigid, durable material such as,but not limited to, metal, plastic, a composite material or the like.According to one embodiment, with reference to FIG. 28, the top of thesystem is positioned above the ocean surface to, for example, provide aplatform on which a wind turbine can be supported. According to otherembodiments, the system may be completely submerged in the aquatic body,to reduce the susceptibility of the system to wind and tidal forces.

With reference to FIG. 29, a method of storing energy according to oneembodiment will now be described. As shown in step 291, a storage weightis elevated against gravity from a first elevation to a second elevationduring an off-peak period, when energy demand is lower relative to apeak period. As such, the gravitational potential energy of the storageweight is increased. As shown in step 292, the gravitational potentialenergy of the storage weight is maintained for release during a peakperiod. According to a further embodiment, as shown in step 293, thegravitational potential energy of the storage weight is released duringthe peak period. The storage weight may be lowered with gravity suchthat its gravitational potential energy is released.

Embodiments of the present invention are directed to energy storagesystems that can serve as reliable, dispatchable baseload powersupplies, as well as intermittent power supplies. In particularembodiments, the systems may harness energy produced by renewablesources, such as that collected by solar collectors and wind turbines.According to embodiments of the present invention, a significantfraction of the output from solar and/or wind sources is directed intolarge-scale energy storage units, which may then release that energy ata later time (e.g., on an as-needed basis).

Although certain embodiments that have been described above are directedto systems by which “off-peak” energy is stored for subsequent “peak”usage, embodiments of the invention are also directed to systems forfrequency regulation, or regulation, of energy generation. In suchsystems, differences between the levels of the energy generated and thelevels of energy demanded are balanced to reduce or minimize suchdifferences. According to such embodiments, the path along which astorage weight (e.g., a weight similar to storage weight 202 of FIG. 2)may travel may have a suitable vertical length such as, but not limitedto, a length of around 200 meters or more. In a particular embodiment,the vertical length of the path is between approximately 200 meters and400 meters.

The foregoing description of certain embodiments of the invention hasbeen presented for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Many modifications and variations are possible in lightof the above teachings. Therefore, it is intended that the scope of theinvention be limited not by this detailed description, but rather by theclaims appended hereto.

1. A system for storing energy, the system comprising: at least onebody; a hollow shaft structure having an interior volume for containinga fluid, the at least one body being disposed within the interior volumeof the hollow shaft structure for movement with gravity from a firstelevation position to a second elevation position within the interiorvolume of the hollow shaft structure; a fluid return path structurecoupled in fluid flow communication with the hollow shaft structure, forcommunicating fluid with a first portion of the interior volume of thehollow shaft structure, the first portion of the interior volume of thehollow shaft structure being located vertically below the at least onebody; and an electrical energy generator operatively coupled with thefluid return path structure to drive the electrical energy generator togenerate electricity upon movement of the at least one body with gravityfrom the first elevation position to the second elevation position;wherein the at least one body comprises a plurality of bodies, andwherein the system further comprises a structure for suspending each ofthe bodies and selectively releasing the bodies for individual movementwith gravity from the first elevation position to the second elevationposition.
 2. The system of claim 1, wherein the suspending structurecomprises a plurality of latches, each of the latches selectivelyconfigurable to engage one of the bodies.
 3. The system of claim 1,further comprising a fluid pump or turbine coupled in fluidcommunication with the fluid return path structure and mechanicallyconnected with the electrical energy generator, for receiving fluidpressure from the fluid return path structure and driving the electricalenergy generator to generate electricity upon movement of the at leastone body by gravity from the first elevation position to the secondelevation position.
 4. The system of claim 1, further comprising a fluidpump or turbine coupled in fluid communication with the fluid returnpath structure and mechanically connected with the electrical energygenerator, wherein the electrical energy generator has an electricalmotor mode for driving the fluid pump or turbine to force fluid into thereturn path structure and increase fluid pressure in the first portionof the interior volume of the hollow shaft structure by an amountsufficient to move the at least one body from the second elevationposition toward the first elevation position.
 5. The system of claim 1,wherein the return path structure comprises a fluid pipe coupled at oneend to the first portion of the hollow shaft structure and at a secondend to a fluid pump or turbine.
 6. The system of claim 1, furthercomprising a fluid pump or turbine coupled in fluid communication withthe fluid return path structure and mechanically connected with theelectrical energy generator, wherein the return path structure comprisesa fluid pipe coupled at one end to the first portion of the hollow shaftstructure and at a second end to the fluid pump or turbine, forconveying fluid pressure between the first portion of the hollow shaftstructure and the fluid pump or turbine.
 7. The system of claim 1further comprising at least one seal arranged to inhibit fluid flowacross the at least one body, between the first portion of the interiorvolume of the hollow shaft structure and a second portion of theinterior volume of the hollow shaft structure that is located verticallyabove the at least one body.
 8. The system of claim 1, wherein a secondportion of the hollow shaft structure that is located vertically abovethe at least one body, is in fluid flow communication with the returnpath structure.
 9. The system of claim 8, further comprising a pumpturbine arranged in fluid flow communication between the second portionof the hollow shaft structure and the return path structure.
 10. Thesystem of claim 9, wherein the electrical energy generator isoperatively coupled to the pump turbine to selectively drive the pumpturbine.
 11. The method of claim 1, wherein a second portion of thefluid container is located vertically above the at least one body and isin fluid flow communication with the return path structure, the methodfurther comprising arranging a pump turbine in fluid flow communicationbetween the second portion of the hollow shaft structure and the returnpath structure.
 12. The method of claim 11, wherein the electricalenergy generator has a drive mode and wherein coupling the electricalenergy generator comprises operatively coupling the electrical energygenerator to the pump turbine to selectively drive the pump turbine. 13.A system of claim 1, wherein each body includes a fluid flow passagethrough which fluid flows when the body is suspended, the system furtherincluding a valve associated with the fluid flow passage of each body toselectively open and close the fluid flow passage.
 14. The system ofclaim 13, wherein the valve is operated to selectively open the fluidflow passage of one of the bodies when that body is suspended astationary and to selectively close the fluid flow passage of the bodywhen the body is released for movement from the first elevation positionto the second elevation position.
 15. A system for storing energy, thesystem comprising: at least one body; a link for suspending the at leastone body for movement with gravity from a first elevation position to asecond elevation position; and an electrical energy generator coupledwith the at least one body through the link to drive the electricalenergy generator to generate electricity upon movement of the at leastone body with gravity from the first elevation position to the secondelevation position, an operator configured to operate the link tocontrollably move the at least one body against gravity from the secondelevation position to the first elevation position to increase agravitational potential energy of the at least one body, and to maintainthe gravitational potential energy of the at least one body, wherein thelink is for suspending the at least one body for movement againstgravity from the second elevation position to the first elevationposition; a buoyant platform for supporting the operator on water; and awind turbine supported on the buoyant platform and coupled with theoperator for powering the operator to operate the link.
 16. The systemof claim 15, wherein the link comprises at least one of a cable, a wire,a rope, a belt and a chain.
 17. The system of claim 15, wherein the linkis for suspending the at least one body for movement with gravity alongan underwater path.
 18. The system of claim 17, wherein the buoyantplatform is configured for supporting the link on water.
 19. The systemof claim 18, wherein the buoyant platform comprises a ballast tankpositioned on the buoyant platform, the ballast tank configurable toreceive water to change a center of gravity of the platform.
 20. Thesystem of claim 15, wherein the operator comprises a hoist.
 21. Thesystem of claim 15, wherein the wind turbine comprises a tower; andwherein the buoyant platform defines a chamber for slidably receivingthe tower of the wind turbine.
 22. A method for storing energy, themethod comprising: providing a link for suspending at least one body formovement with gravity from a first elevation position to a secondelevation position; coupling an electrical energy generator with the atleast one body through the link to drive the electrical energy generatorto generate electricity upon movement of the at least one body withgravity from the first elevation position to the second elevationposition; configuring an operator to operate the link to controllablymove the at least one body against gravity from the second elevationposition to the first elevation position to increase a gravitationalpotential energy of the at least one body, and to maintain thegravitational potential energy of the at least one body; providing abuoyant platform for supporting the operator on water, and supporting awind turbine on the buoyant platform and coupling the wind turbine withthe operator for powering the operator to operate the link.